Donald Trump has said he'd like to put H&R Block out of business. He regularly maligns Ford, Nabisco and Carrier for sending U.S. jobs overseas. And, most notoriously, he's called for forcibly removing millions of Mexican immigrants and barring Muslims from entering the country.

Now, after sustaining months of put-downs, the targets of Trump's attacks are starting to take the front-runner seriously by fighting back in Washington. A shift is underway: Instead of continuing to brush off Trump, companies and their representatives in D.C. are executing plans to protect their reputations among lawmakers, cognizant that criticism from the GOP front-runner is having an effect.

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“To scoff at anything Trump says is a foolish place to be in Washington anymore. People have to take it seriously,” said Lisa Camooso Miller, a former Republican National Committee spokeswoman now at Blueprint Communications.

Representatives for Ford have been highlighting the automaker's 80,000 American workers to lawmakers who ask about Trump's claims that the company is building cars in Mexico. They tout plans to invest some $9 billion over the next four years in the United States, on top of the billions the company has already spent in the country.

A Mexican government official said an effort is afoot to inform the media, lawmakers and other U.S. officials about the contributions the country makes to the American economy and the importance of its bilateral relationship with the U.S. Trump's signature campaign promise is to build a wall along the U.S.-Mexico border.

"The Mexican government considers Mr. Trump as an ignorant and racist person," the official said. "And that he obviously is not very well-informed about Mexico and Mexicans."

The fallout extends to the Republican National Convention. At least one company that's been on the receiving end of Trump's wrath, H&R Block, is skipping the convention in Cleveland. Other firms targeted by Trump, such as Ford, won’t say whether they'll have a presence at the event, which is just three months away. Ford participated in the 2012 GOP convention in Tampa, Florida; H&R Block did not.

“We believe the best use of our resources is to continue focusing on serving our clients,” said H&R Block spokesman Gene King. The decision comes as Trump regularly has been sounding off on the campaign trail against the Kansas City-based tax preparation company, saying time and again that he wants to “put H&R Block out of business" as part of his plan to simplify the tax code.

Under attack, H&R Block hasn’t tried to hit back at Trump in the media. But it has worked to keep up its image on Capitol Hill by reminding lawmakers that the company has a presence and employees in every congressional district.

“Any serious discussion about simplification [of the tax code] needs to include a balanced and considered conversation of how important programs like these will be administered outside of the tax code. That’s a job for Congress,” King said.

Carrier, which has perhaps been the subject of Trump's most pointed attacks, declined to discuss the front-runner's criticism or respond to questions about whether it would participate in the GOP convention.

One in-house lobbyist for a Fortune 500 company that has come under fire from Trump said the playbook for pushing back against the real estate magnate is "marketing 101."

"It's about redoubling of efforts to make sure you are explaining why as a corporation you exist, what your value add is ... making sure that you have existing relationships with members and their staff," the lobbyist said.

Several crisis communications consultants said it’s important for companies to continue to focus on their core missions, but at the same time to be alert to any damage Trump's words could be doing.

"I think most brands are protective of the reputation that they’ve built for themselves, and they are going to be very thoughtful about whether or not they want to be associated in one way or another with the political conventions, and that’s to the detriment of the party," Camooso Miller said of the possibility that corporations will stay away from a Trump-filled convention.

"It takes that support from the corporate community to make it successful so without having that corporate backing it could make it end up even more of a circus than I think it probably already will be."

Rich Masters, a veteran public relations expert at Qorvis Communications, said he is counseling clients to "mainly stick to your message and make sure you are always on and listening."

Qorvis represents countries including Saudi Arabia, Mexico and China, which have all been targeted by Trump. In some cases, Masters said there could actually be opportunity in enduring a Trump lashing.

“Frankly, Mexico has a great story to tell, and the trade stuff is also very good, so this is also a potential opportunity for clients as well," he said.

Groups representing the roughly 3 million U.S. Muslims say they are working overtime to educate the public and sign up voters to defeat Trump. The Council on American-Islamic Relations' Robert McCaw said the group has made public calls and written letters to Trump to meet with Muslim community leaders after he asserted, with no apparent evidence,that American Muslims cheered the Twin Towers collapsing on Sept. 11.

The group is bringing some 280 delegates to Capitol Hill on April 18 for its second annual Muslim advocacy day, and it moved to register 20,000 voters before Super Tuesday.

"There is a high concentration of American Muslim voters in swing states like Virginia, Florida and Ohio. We have the ability to tip elections," McCaw said. "That's something candidates like Trump and Ted Cruz need to seriously consider."

Groups such as Color of Change have been pressuring companies like Coca-Cola to try and get them to pull their financial support from the Republican convention because of Trump. Representatives from the soda company have said it gives to both conventions because it is an important part of the political process and that the company doesn't endorse any presidential candidates.

Rashad Robinson, executive director for the group, said Color of Change is moving into the next phase of its campaign by enlisting groups representing women, Muslims and others to lean on the company.

Republican Party officials insist that companies and others continue to financially support the convention. Last week, for instance, AT&T was named the official telecommunications provider for the convention.

But some trade groups that have traditionally contributed big dollars to the convention are holding out, not declaring whether they will pony up this time around.

The American Petroleum Institute was one of the largest private contributors during the most recent presidential election cycle, cutting a $1 million check for the 2012 convention. The oil industry group won't disclose its plans for the Republican convention.

"I don't have any information on 2016 at this time," API spokesman Eric Wohlschlegel said when asked what the group would be doing in Cleveland.

Cleveland's host committee is committed to raising $64 million for the event. It has not publicly released its financial backers beyond JobsOhio ($10 million), the City of Cleveland ($2.5 million) and Cuyahoga County ($2.5 million). Convention organizers have struggled in the past to raise enough funds, turning to major donors such as New York Jets owner Woody Johnson to help make up the difference.

GOP convention spokeswoman Kirsten Kukowsi did not respond to several requests for comment. She said in January that there was "growing interest" from donors and media to help fund the event. "Donors are certainly looking at the marketing opportunity a convention will provide, and this convention promises to be a great opportunity regardless of the nominee," Kukowski said at the time.

Emily Lauer, a spokeswoman for Destination Cleveland, the city's convention and tourism agency, said fundraising is continuing apace.

“The Cleveland 2016 Host Committee’s fundraising is on track, and we continue to make forward progress in our fundraising efforts," Lauer said in a statement. "To date, we’ve raised 85 percent of our $64 million goal, and we’re confident that our sponsors are committed to being part of the convention in Cleveland this summer.”